recordreader.java

hadoop:Nutch集群平台

/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.record;

import java.io.IOException;
import java.io.InputStream;
import java.io.DataInputStream;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.SAXException;

/**
 * Front-end interface to deserializers. Also acts as a factory
 * for deserializers.
 *
 * @author Milind Bhandarkar
 */
public class RecordReader {
    
    private InputArchive archive;

    static private HashMap archiveFactory;
    
    static {
        archiveFactory = new HashMap();
        Class[] params = { InputStream.class };
        try {
            archiveFactory.put("binary",
                    BinaryInputArchive.class.getDeclaredMethod(
                        "getArchive", params));
            archiveFactory.put("csv",
                    CsvInputArchive.class.getDeclaredMethod(
                        "getArchive", params));
            archiveFactory.put("xml",
                    XmlInputArchive.class.getDeclaredMethod(
                        "getArchive", params));
        } catch (SecurityException ex) {
            ex.printStackTrace();
        } catch (NoSuchMethodException ex) {
            ex.printStackTrace();
        }
    }
    
    static private InputArchive createArchive(InputStream in, String format)
    throws IOException {
        Method factory = (Method) archiveFactory.get(format);
        if (factory != null) {
            Object[] params = { in };
            try {
                return (InputArchive) factory.invoke(null, params);
            } catch (IllegalArgumentException ex) {
                ex.printStackTrace();
            } catch (InvocationTargetException ex) {
                ex.printStackTrace();
            } catch (IllegalAccessException ex) {
                ex.printStackTrace();
            }
        }
        return null;
    }
    /**
     * Creates a new instance of RecordReader.
     * @param in Stream from which to deserialize a record
     * @param format Deserialization format ("binary", "xml", or "csv")
     */
    public RecordReader(InputStream in, String format)
    throws IOException {
        archive = createArchive(in, format);
    }
    
    /**
     * Deserialize a record
     * @param r Record to be deserialized
     */
    public void read(Record r) throws IOException {
        r.deserialize(archive, "");
    }
    
}